Thin polished plates such as silicon wafers and the like are a very important part of modern technology. A wafer, for instance, refers to a thin slice of semiconductor material used in the fabrication of integrated circuits and other devices. Other examples of thin polished plates may include magnetic disc substrates, gauge blocks and the like. Modern semiconductor devices are typically fabricated from layers of semiconductor, conductor or isolator material printed on wafers using photolithography techniques. Precise positioning and alignment during semiconductor fabrication is of critical importance.